Cervelo has updated its S5 aero road bike for 2015, with 31 improvements over the old Cervelo S5 VWD model. These include an increase in stiffness at the bottom bracket area of 35 per cent – making it nearly as stiff as the R-series – and a claimed saving of 21.3 watts at 40km per hour, while keeping the frame weight down to 1,065g.
Cervelo S5 2015 frame changes
From a side-on perspective, the new S5 frame looks nearly identical to the old version, but Cervelo has made several changes during the redevelopment of its flagship aero road platform. The most notable are the increase in diameter – and stiffness — of the head tube, a decrease in the head tube height, and the increased tyre clearance to accept 25mm tyres.
The fork now has a tapered steerer (1 1/8 to 1 3/8in), which has helped stiffen up the front end – the old bike was a little soft in steering, as we found in our own testing. The stack height has been lowered too (down to 565mm on our 56cm test bike), to allow more aggressive riding positions.
An aerodynamic study conducted by the Canadian company found that top tubes and chainstays have no effect on the drag of the frame, so the new S5 has the same tubes here as the R5CA. This also means the rear derailleur cable exits from the end, right next to the derailleur. The seat tube has been widened; Cervelo started at the UCI minimum and built out until it hit an aerodynamic sweet spot.
The seatpost itself comes with a 20mm offset. A two-position version, that offers 0 and 40mm setups, is also available. There's also the option of a taller clamp for thicker carbon-braided rails. Cervelo has done away with the internal guide tubes for the hidden cables, and instead lengthened the trailing edge of the head tube and used a plastic guide to feed the cables though, with no kinking to affect shifting performance.
The frame is compatible with electronic and mechanical setups. Cervelo has chosen to use Shimano's long cyclindrical seatpost battery for Di2, but this is housed in the down tube, because it doesn’t fit in the seatpost.
The S5 uses Cervelo's BBright standard, which allows an asymmetric frame design
The BBright bottom bracket means the frame is tailored asymmetrically for stiffness, and this carries to the seatstays too. The non-driveside stay meets the axle in as straight a line as possible while the driveside features a slight kink outwards, which Cervelo says allows extra clearance for the dynamic movement of shifting gears.
The biggest gain in aerodynamics comes at the handlebar, which represent Cervélo’s first foray into building the component. Internal CFD testing found that handlebars typically account for 30 percent of a bike’s total drag, so the company started work there.
The radically shaped bar uses a fairly conventional 80mm reach and 128mm drop, but the tops are huge and flat – right up against the UCI’s 3:1 ratio. The neatly channelled cable integration keeps everything smooth, and the angular cuts at the bars elbow into the hood gives plenty of wrist clearance when riding the in the drops.
“The real challenge was to balance the incredible potential shown by some of our more disruptive designs with real-world needs, such as accommodating a standard 31.8 stem,” said Graham Shrive, Cervelo’s lead engineer on the S5. “When tested using our standard protocols, we found it gave a 4.4-watt advantage over an identically configured round bar.”
The bars clamp to a standard stem, which Cervelo found to be faster than an aero model
The bars fit a standard 31.8mm stem and Cervelo says that a regular stem actually tested faster than an aero one. The bar comes as standard on complete bikes (but not the frameset), and are also available as an aftermarket component for US$400 / £339.
The bar does not have an obvious place to mount a Garmin or other bike computer, but Cervelo claims that mounting the Garmin on top of the stem is faster in a wind tunnel than out in front. (Bontrager has an integrated mount solution on the underside of its XXX Integrated Bar/Stem that can be configured for Garmin computers or other peripherals.)
Wheels and spec
Cervelo is selling the same frame and forks on all three versions of the new S5, using HED Jet+ 60mm wheels on the Dura-Ace and Dura-Ace Di2 models, with the mechanical Ultegra model being supplied with Mavic Cosmic 30mm wheels.
Cervelo says the use of the Jet+ wheels, with their aluminium brake track, means that the rim itself is wider, allowing the clincher tyres to sit very slightly further apart than on a carbon clincher, which flattens the tyre to improve aerodynamics – and make for a more comfortable ride.
Specs and pricing
- Cervelo S5 Shimano Dura-Ace Di2 US$10,000 / £7,299 / AU$11,000
- Cervelo S5 Shimano Dura-Ace US$8,000 / £5,599 / AU$8,700
- Cervelo S5 Shimano Ultegra US$5,500 / £3,799 / AU$5,800
- Cervelo S5 Frameset US$4,500 / £3,100 / AU$5,300
The bike uses standard Shimano brakes, with the rear brake being secured via a simple bolt-on housing. First seen on the original P3C, this has been tweaked to make mechanical mainenance easier. Cervelo says that mounting the rear brake in its traditional position at the top of the seatstays is easier to maintain and also reduces the chance of wheel rub as this area of the bike deforms in sympathy with the wheel's rim when under stress, whereas the under-the-chainstays section doesn't.
The S5 redesign features a greater surface area than before, but the removal of the guide tubes and use of the carbon layup techniques used on the R5CA mean the frame weight remains around the same level as before at 1,065g – perhaps a little hefty when placed against some other new aero road machines, but with the weight going towards a claimed saving of 21.3 watts at 40km per hour, plus a 35 per cent increase in stiffness, it hardly seems like a penalty.
Cervélo now claims that the S5 has very similar stiffness and strength figures as its R series machines, and that’s no mean feat when dealing with complex narrow aero profiles. By using internal bulkheads and blending compaction and moulding techniques only previously found on RCA and VWD level machines, the new S5 is VWD standard and Cervélo has no plans to introduce a higher VWD version.BikeRadar.com News: http://feedproxy.google.com/~r/BikeRadar/Road/News/~3/DD3hIWtd4fY/story01.htm